Lightning. It avoids the ocean, but likes Florida. Its attracted to the Himalayas and even more so to central Africa. And lightning almost never strikes the north or south poles.

These are just a few of the things NASA scientists have learned using satellites to monitor worldwide lightning.

For the first time, weve been able to map the global distribution of lightning, noting its variation as a function of latitude, longitude and time of year, says Hugh Christian, project leader for the National Space Science and Technology Centers (NSSTCs) lightning team at NASAs Marshall Space Flight Center.

This new perspective on lightning is possible thanks to two satellite-based detectors: the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS). The OTD and the LIS are two optical sensors that weve flown in lower Earth orbit, says Christian, whose team developed the sensors. The OTD was launched in 1995 and we got five good years out of it. The LIS was launched on the Tropical Rainfall Measuring Mission satellite in 1997 and its still going strong."

Basically, these optical sensors use high-speed cameras to look for changes in the tops of clouds, changes your eyes cant see, he explains. By analyzing a narrow wavelength band around 777 nanometerswhich is in the near-infrared region of the spectrumthey can spot brief lightning flashes even under daytime conditions.